A single blind prospective Randomised Controlled Trial (RCT) to investigate the need for a transition phase following successful completion of functional appliance therapy and a sample size calculation pilot study

Aims: The aim of this study was to investigate whether transition following successful completion of functional appliance therapy was important in retention of the corrected overjet. Objectives: The main objective was to investigate whether a transition phase following successful completion of functional appliance therapy was important in retention of the corrected overjet. In addition, a secondary objective was to perform a pilot study to aid in a sample size calculation for a larger trial to investigate the effect of transition versus no transition following successful completion of functional appliance therapy. Method: Patients were randomly allocated to either Group A (Standard care) or Group B (intervention). They were then followed up monthly for a period of three months. At each monthly visit, clinical measurements of overjet were taken. At the end of this period the clinical measurements were analysed by a blinded assessor who was unaware of the allocation of the treatment. Outcome measures: The primary outcome variable was the presence/absence of a corrected overjet at the end of the study within 2mm of the overjet at the end of Twin Block therapy. The overjet measurements were based on clinical findings. Results: • The recruited sample was primarily female at 66.6% compared to males at 33.3%. Females were shown to have a higher success rate than males at 80%; however these results were not significant. • The average overjet in Group A was 7.1 mm. The average overjet of the successful patients in Group A was 7.3 mm and 7 mm in the unsuccessful patients. • The average overjet in Group B was 10.5 mm. The average overjet in the successful patients in Group B was 11.3 mm and 9.3 mm in the unsuccessful patients. • In Group A, 1 successful and 1 unsuccessful patient attended the casuals' clinic. In Group B, 3 successful and 1 unsuccessful patients attended the casuals' clinic. • In the total sample only 1 patient cancelled an appointment, this appointment was subsequently rearranged for within 2 weeks of original date. • In the total sample only 1 patient failed to attend an appointment. • All patients in the study had a Dental Health Component (DHC) of either a 4a or 5a. 33.3% had a DHC component of a 5a and 66.66% had a 4a. • A Fisher's exact test was carried out to compare the proportions with retention of the corrected overjet. The p value was 0.643 (Appendix 1) which was substantially higher than the 0.05 level of statistical significance set for this study. Conclusion: 1. The null hypothesis could not be rejected based on the results of this study. Therefore, there is no evidence of difference in using any form of transition following successful completion of functional appliance therapy compared to no transition. 2. A secondary objective of this study was to investigate the size of sample size needed to appropriately power a project of this type. This was measured to 97 patients per group with α set at 80% and significance level of 0.05. 3. Due to the small sample size, the study was not powered to detect a clinical significance difference between the groups and therefore it is not possible to determine if the intervention is better at maintaining the control group than the standard care group 4. This pilot did not give sufficient information to accurately estimate the proportion of successful retention of the overjet in the transition group. 5. The investigation was not continued after the doctoral project was complete due to problems with recruitment and lack of personnel to continue the study.